High-speed digital circuitry is commonly packaged in compact circuit modules which contain a number of complex integrated circuits. Such circuit modules generate large amounts of heat in a relatively small volume. Since digital circuits conduct current primarily during transitions between logic states, power requirements increase with operating speed. An additional factor that tends to increase heat dissipation in high-speed digital circuits is that the circuit components must be packaged in close proximity to each other in order to avoid the undesirable effects of long interconnecting leads. The parasitic capacitance and inductance of interconnecting leads can cause unacceptable delays when the circuit components are not carefully packaged. Therefore, high speed digital circuits are typically packaged in a compact circuit module with the spacing between components minimized. Such circuit modules may generate several hundred watts in a module having dimensions of only a few inches on a side. Efficient removal of thermal energy is necessary in order to maintain the circuit components within their rated operating temperature limits.
Prior art circuit cooling technigues have included heat sinks with air cooling, heat sinks with a recirculating liquid and cryogenic techniques. While liquid and cryogenic techniques provide highly efficient heat transfer, these techniques are complex and expensive. For example, liquid cooling requires a pump, a heat exchanger, a heat sink and interconnecting conduits. Leaks in the cooling system may damage other system components and are costly to repair. While air-cooled systems are simpler and less expensive, prior art air-cooled systems have not been adequate to handle the heat loads of high-speed digital circuit modules. Other disadvantages associated with prior art air-cooled systems include the acoustic noise associated with air flow and nonuniform cooling over the area of the circuit module.
Heat sinks commonly have multiple fins for increasing the area of heat transfer to a cooling medium. The increased heat transfer available with heat sinks having narrow channels, or microchannels, between fins is described by N. Goldberg in "Narrow Channel Forced Air Heat Sink", IEEE Transactions 0n Components, Hybrids, And Manufacturing Technology, Vol. CHMT 7, No. 1, March 1984, pp. 154-159 and by D. B. Tuckerman et al in "High Performance Heat Sinking for VLSI", IEEE Electron Device Letters, Vol. EDL-2, No. 5, May 1981, pp 126-129. While these designs provide improved heat transfer capability, they are inadequate for cooling high heat-dissipation circuit modules.
It is a general object of the present invention to provide apparatus for improved cooling of electronic circuit modules and other heat-generating objects.
It is another object of the present invention to provide heat sinks capable of handling large heat loads.
It is a further object of the present invention to provide heat sinks which maintain a relatively uniform temperature distribution over the area of the object being cooled.
It is yet another object of the present invention to provide air-cooled heat sinks capable of handling large heat loads.
It is a further object of the present invention to provide high capacity air cooled heat sinks wherein the generation of objectionable acoustic noise is limited.
It is a further object of the present invention to provide high capacity heat sinks which are low in cost and easy to manufacture.
It is a further object of the present invention to provide high capacity heat sinks which are easily adapted to different cooling requirements.